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KVM: X86: Yield to IPI target if necessary

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When sending a call-function IPI-many to vCPUs, yield if any of
the IPI target vCPUs was preempted, we just select the first
preempted target vCPU which we found since the state of target
vCPUs can change underneath and to avoid race conditions.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wanpeng Li 2019-06-11 20:23:48 +08:00 committed by Paolo Bonzini
parent 11e349143e
commit f85f6e7bc9
4 changed files with 34 additions and 0 deletions
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11
Documentation/virtual/kvm/hypercalls.txt
View File

@ -141,3 +141,14 @@ a0 corresponds to the APIC ID in the third argument (a2), bit 1
corresponds to the APIC ID a2+1, and so on.
Returns the number of CPUs to which the IPIs were delivered successfully.
7. KVM_HC_SCHED_YIELD
------------------------
Architecture: x86
Status: active
Purpose: Hypercall used to yield if the IPI target vCPU is preempted
a0: destination APIC ID
Usage example: When sending a call-function IPI-many to vCPUs, yield if
any of the IPI target vCPUs was preempted.

1
arch/x86/include/uapi/asm/kvm_para.h
View File

@ -30,6 +30,7 @@
#define KVM_FEATURE_ASYNC_PF_VMEXIT 10
#define KVM_FEATURE_PV_SEND_IPI 11
#define KVM_FEATURE_POLL_CONTROL 12
#define KVM_FEATURE_PV_SCHED_YIELD 13
#define KVM_HINTS_REALTIME 0

21
arch/x86/kernel/kvm.c
View File

@ -527,6 +527,21 @@ static void kvm_setup_pv_ipi(void)
pr_info("KVM setup pv IPIs\n");
}
static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
{
int cpu;
native_send_call_func_ipi(mask);
/* Make sure other vCPUs get a chance to run if they need to. */
for_each_cpu(cpu, mask) {
if (vcpu_is_preempted(cpu)) {
kvm_hypercall1(KVM_HC_SCHED_YIELD, per_cpu(x86_cpu_to_apicid, cpu));
break;
}
}
}
static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
{
native_smp_prepare_cpus(max_cpus);
@ -638,6 +653,12 @@ static void __init kvm_guest_init(void)
#ifdef CONFIG_SMP
smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;
smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
if (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) &&
!kvm_para_has_hint(KVM_HINTS_REALTIME) &&
kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi;
pr_info("KVM setup pv sched yield\n");
}
if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
kvm_cpu_online, kvm_cpu_down_prepare) < 0)
pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");

1
include/uapi/linux/kvm_para.h
View File

@ -28,6 +28,7 @@
#define KVM_HC_MIPS_CONSOLE_OUTPUT 8
#define KVM_HC_CLOCK_PAIRING 9
#define KVM_HC_SEND_IPI 10
#define KVM_HC_SCHED_YIELD 11
/*
* hypercalls use architecture specific